Every week, COSMOS: A Spacetime Odyssey celebrates Earth’s abundant forms of life, from the birth of living organisms to humans’ existence today. But in tonight’s episode, it looks at how our civilization may die.

The episode doesn’t get too gloomy with its doomsday predictions, postulating a few possible ends to life on Earth. Some ends are more plausible, while others – like a massive volcanic winter – aren’t as likely to strike. Luckily for us, COSMOS doesn’t predict our universe ending anytime soon, but some ends are more immediate than others.

1. An Earth-Melting Supernova

Supernovas = the worst possible outcome.

Let’s start with the bad news: if a stellar explosion happened anywhere less than 30 light years away from Earth, the supernova’s cosmic radiation would destroy our atmosphere’s protective ozone layer, bringing an unavoidable end to our civilization. Somewhere in our universe, a star explodes every second.

Stars can go supernova in two possible ways. Type I supernovas occur when white dwarf stars, or dead star husks that have exhausted their energy, accumulate gasses from a companion star until a runaway nuclear reaction occurs, igniting the star into an explosion. Type II supernovas are more dramatic. A star must be far larger than our Sun (estimated at eight to 15 solar masses) to supernova this way, collapsing under its own gravity once it runs out of nuclear fuel.

The good news for all life on Earth? This supernova modeled above occurred over 1,000 light years away from us, and they’re likely to stay that far away. None of the stars close enough to harm the Earth are likely to go supernova any time in the next few hundred million years, so we’re safe from now.

2. A Massive Volcanic Winter

Can a supervolcano spew out enough ash to obfuscate the Sun and end all human life? It’s happened before.

Every million years or so, a giant volcano erupts somewhere on Earth, most recently on the island of Sumatra (present-day Indonedia) 74,000 years ago. The explosion emitted hundreds of times more rock, ash and toxic gas than any other volcano in recorded history, sending more than 600 cubic miles of pulvarized rock into the sky. As winds carried this ash over the Indian subcontinent, the sulfuric gasses emitted into the atmosphere created a global haze, blocking sunlight from reaching the Earth. The cloud didn’t budge for over five years, as temperatures fell globally and much of Earth’s life was wiped out.

If an explosion like the Sumatran volcano happened in the near future, humans would likely survive, but our civilization as we know it would be destroyed. However, Neil deGrasse Tyson postulates on COSMOS that while another massive volcanic eruption may be inevitable, our scientific advances of the future may be able to siphon off the supervolcano’s energy, preventing an explosion – and even, with more advanced science, potentially prevent a supernova too.

3. A Rampant Disease Outbreak

While advanced science may enable researchers to prevent a supernova or massive volcano, civilizations of the past have been wiped out by devastation they couldn’t see coming.

Christopher Columbus and the European invaders of Central and South America traveled to the region to conquer the land with their valor and advanced weaponry. However, their most powerful weapons weren’t ones they could control. Nearly 9 in 10 of the Americas’ native population died from bacteria and viruses the invaders carried over from Europe, as they were exposed to smallpox and other diseases the indigenous peoples had never before encountered.

The great civilizations of the New World were no match for the armies of pathogens the invaders brought with them. So far, our modern civilization has yet to encounter a disease outbreak of that scale. Will science be able to see a massive pandemic coming? The invisible danger of disease outbreak is more present than a supernova, that’s for sure.

4. Global Climate Change

Whether it’s freak environmental disaster or a widespread pandemic, human life is endangered by forces we can’t control. But Neil deGrasse Tyson looks at one last devastating end to civilization, one that’s very different from the others.

Yes, he’s talking about ours. What happens to the human race when it willingly tanks its chances at longevity? “The prevailing economic systems, no matter what their ideologies, have no built-in mechanisms for protecting our descendants of even 100 years from now, let alone 100,000,” Tyson says. We know our tiny Earth’s resources aren’t infinite, and scientific consensus agrees our actions are destabilizing our climate.

Comments

Barry Vacker

Temple University, Philadelphia

May 19, 2014, 7:10 pm

“Immortals” was an excellent episode, joining a long line of science-based apocalyptic scenarios for humans and/or the ecosystems on Earth. Apologies for self-promoting, but I have written a book that is a perfect compansion to this episode: “The End of the World — Again: Why the Apocalypse Meme Replicates in Media, Science, and Culture.”

Stuart Dobson

Melbourne, Australia

May 25, 2014, 8:42 am

“The prevailing economic systems, no matter what their ideologies, have no built-in mechanisms for protecting our descendants..”

This hits the nail on the head.

Our political and economic systems are fundamentally flawed for this reason. We need to create a system with these built-in mechanisms of sustainability if we are to survive. The mechanisms need to incentivize sustainability and social progress in the same way that the current system incentivizes profit at the expense of everything else.

One step towards this system is the abolition of our abstract financial system which has no association with reality or nature.